A Joint Model of X - Ray and Infrared Backgrounds . Ii . Compton - Thick Agn Abundance

We estimate the abundance of Compton-thick (CT) active galactic nuclei (AGN) based on our joint model of X-ray and infrared backgrounds. At Lrest2−10keV > 10 42 erg/s, the CT AGN density predicted by our model is a few ×10 Mpc from z=0 up to z=3. CT AGN with higher luminosity cuts (> 10, 10 & 10 erg/s) peak at higher z and show a rapid increase in the number density from z=0 to z∼2-3. The CT to all AGN ratio appears to be low (2-5%) at f2−10keV > 10 −15 erg/s/cm but rises rapidly toward fainter flux levels. The CT AGN account for ∼ 38% of the total accreted SMBH mass and contribute ∼ 25% of the cosmic X-ray background spectrum at 20 keV. Our model predicts that the majority (90%) of luminous and bright CT AGN (Lrest2−10keV > 10 44 erg/s or f2−10keV > 10 −15 erg/s/cm) have detectable hot dust 5-10 μm emission which we associate with a dusty torus. The fraction drops for fainter objects, to around 30% at Lrest2−10keV > 10 42 erg/s or f2−10keV > 10 −17 erg/s/cm. Our model confirms that heavily-obscured AGN (NHI > 10 23 cm) can be separated from unobscured and mildly-obscured ones (NHI < 10 23 cm) in the plane of observed-frame X-ray hardness vs. mid-IR/X-ray ratio. Subject headings: galaxies: nuclei – galaxies: active